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Reference
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| Title: |
Report on Referred Fossils
,
1975
(11/03)
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| Report by: |
Ralph W. Imlay
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| Referred by: |
Bela Csejtey
, Jr.
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| | Age: | Early Jurassic |
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| Comment: | The two ammonite fragments from the basal part of the ophilitic squence belong to the family Arietitidae of Sinemurian to early Pliensbachian age. The specimens bear high, sharp, widely-spaced ribs, radial ribs that are slightly swollen ventrally and then terminate abruptly at the ventral margin as in the genus Megarietites. Exact generic identification must await the discovery of specimens that show the charateristics of the venter and of the inner whorls. With these ammonite fragments are two poorly preserved pelecypods of which one bears ribbing suggestive of the Lower Jurassic genus Weyla. Lithologically the specimens at loc. 75ACy-158 are nearly identical with specimens of ammonites and pelecypods that were collected about 8 miles to the southwest (loc. 16229) at the "head of a small eastern tributary that heads against Little Shotgun Creek on west side of Chulitna Valley, north of Elridge Glacier". This collection was made by a prospector Elmer Bedgar and submitted to Ralph Tuck of the Geological Survey in 1932. It contains 20 specimens of ammonites, one specimen of the Lower Jurassic pelecypod Cardinia and one fragment of a Pectinid pelecypod. Eight of the ammonites show the smooth inner whorls and the ventral features that are characteristic of the genus Arnioceras of early Sinemurian age (See Treatise, p. L238). Most of the other specimens belong to the family Arietitidae but are not identifiable generically. The preservation of the fossils at both localities is good enough to warrent extensive and intensive collecting in order to date the ophilitic sequence. |
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